Systems and methods for reduction of atrial fibrillation

ABSTRACT

Embodiments of the present invention are directed to ablation catheter systems configured, for example, to ablate tissue adjacent an ostium of the pulmonary vein in a left atria of a heart. In one embodiment, an ablation catheter system includes a handle including an actuator and a catheter coupled to the handle defining a lumen extending through a length of the catheter, the catheter including a tip portion at a distal end thereof. The ablation catheter system may also include an electrode coupled to the handle with lines extending through the lumen of the catheter, the electrode being configured to be constrained within the tip portion of the catheter and configured to be deployed from the tip portion and self expand to an expanded configuration. With this arrangement, the electrode is configured to self expand to a conical configuration with a tip portion configured to be disposed within the pulmonary vein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/359,223,filed Jan. 23, 2009, and entitled SYSTEMS AND METHODS FOR REDUCTION OFATRIAL FIBRILLATION, pending, which claims the priority of provisionalapplication Ser. No. 61/023,378, filed Jan. 24, 2008, and provisionalapplication Ser. No. 61/114,863, filed Nov. 14, 2008, the disclosures ofeach of which are also incorporated by reference herein in theirentireties.

TECHNICAL FIELD

The present invention relates generally to ablation systems and methodsand, more specifically, to systems and methods for reduction of atrialfibrillation including various electrode configurations and ablationcatheter systems.

BACKGROUND

The heart includes a number of pathways that are responsible for thepropagation of signals necessary to produce continuous, synchronizedcontractions. Each contraction cycle begins in the right atrium where asinoatral node initiates an electrical impulse. This impulse thenspreads across the right atrium to the left atrium, stimulating theatria causing them to contract. The chain reaction continues from theatria to the ventricles by passing through a pathway known as theatrioventricular (AV) node or junction, which acts as an electricalgateway to the ventricles. The AV junction delivers the signal to theventricles while also slowing or delaying it, so the atria can relaxbefore the ventricles contract.

Disturbances in the heart's electrical system may lead to variousrhythmic problems that can cause the heart to beat irregularly, too fastor too slow. Irregular heart beats, or arrhythmia, are caused byphysiological or pathological disturbances in the discharge ofelectrical impulses from the sinoatrial node, in the transmission of thesignal through the heart tissue, or by spontaneous, unexpectedelectrical signals generated within the heart. One type of arrhythmia istachycardia, which is an abnormal rapidity of heart action. There areseveral different forms of atrial tachycardia, including atrialfibrillation and atrial flutter. With atrial fibrillation, instead of asingle beat, numerous electrical impulses are generated by depolarizingtissue at one or more locations in the atria (or possibly otherlocations). These unexpected electrical impulses produce irregular,often rapid heartbeats in the atrial muscles and ventricles. Patientsexperiencing atrial fibrillation may suffer from fatigue, activityintolerance, dizziness and even strokes.

The precise cause of atrial fibrillation, and in particular thedepolarizing tissue causing “extra” electrical signals, is currentlyunknown. As to the location of the depolarizing tissue, it is generallyagreed that the undesired electrical impulses often originate in theleft atrial region of the heart. Recent studies have expanded upon thisgeneral understanding, suggesting that nearly 90% of these “focaltriggers” or electrical impulses are generated in one (or more) of thefour pulmonary veins (PV) extending from the left atrium. In thisregard, as the heart develops from an embryotic stage, left atriumtissue may grow or extend a short distance into one or more of the PVs.It has been postulated that this tissue may spontaneously depolarize,resulting in an unexpected electrical impulse(s) propagating into theleft atrium and along the various electrical pathways of the heart.

A variety of different atrial fibrillation treatment techniques areavailable, including drugs, surgery, implants, and catheter ablation.While drugs may be the treatment of choice for some patients, drugstypically only mask the symptoms and do not cure the underlying cause.Implantable devices, on the other hand, usually correct an arrhythmiaonly after it occurs, but do not cure the condition or preventarrhythmias from occurring again in the future. Surgical andcatheter-based treatments, in contrast, will actually cure the problemby ablating the abnormal tissue or accessory pathway responsible for theatrial fibrillation. The catheter-based treatments rely on theapplication of various destructive energy sources to the target tissue,including direct current electrical energy, radiofrequency (R)electrical energy, laser energy, and the like. The energy source, suchas an ablating electrode, is conventionally disposed along a distalportion of a catheter.

Most ablation catheter techniques employed to treat atrial fibrillationfocus upon locating the ablating electrode, or a series of ablatingelectrodes, along extended target sections of the left atrium wall.Because the atrium wall, and thus the targeted site(s), is relativelytortuous, the resulting catheter design includes multiple curves, bends,extensions, etc. In response to recent studies indicating that theunexpected electrical impulses are generated within a PV, efforts havebeen made to ablate tissue within the PV itself. Obviously, the priorcatheter designs incorporating convoluted, multiple bends are notconducive to placement within a PV. Instead, a conventional “straightended” ablation catheter has been employed. While this technique oftissue ablation directly within a PV has been performed with somesuccess, such a technique is tedious and in not time efficient. As such,an improved ablation catheter that is more conducive to the anatomy andis more time efficient than the conventional “straight ended” ablationcatheter would be desirable.

A related concern entails understanding the electrical characteristicsof the tissue surrounding the PV prior to ablation. For example, foratrial fibrillation, it is necessary to identify the origination pointof the undesired electrical impulses prior to ablation. Typically, anentirely separate catheter is employed for understanding thecharacteristics of the tissue prior to beginning an ablation processwith an ablation catheter. These additional steps greatly increase theoverall time required to complete the procedure.

Based on the foregoing, it is desirable to provide an ablation catheterthat better conforms to the anatomy and overcomes the deficiencies ofthe conventional “straight ended” ablation catheter. Further, it may bedesirable to provide an ablation catheter that does not require theadditional acts that greatly increase the overall time required tounderstand the electrical characteristics of the tissue surrounding thePV.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an ablation catheter systemconfigured, for example, to ablate tissue adjacent an ostium of thepulmonary vein in a left atria of a heart. In one embodiment, theablation catheter system includes a handle including an actuator and acatheter coupled to the handle defining a lumen extending through alength of the catheter, the catheter including a tip portion at a distalend thereof. The ablation catheter system also includes an electrodecoupled to the handle with lines extending through the lumen of thecatheter, the electrode being configured to be constrained within thetip portion of the catheter and configured to be deployed from the tipportion and self expand to an expanded configuration. In one embodiment,the electrode is configured to self expand to a substantially conicalconfiguration with a tip portion configured to be disposed within thepulmonary vein.

In another embodiment, the ablation catheter system includes an energysource coupled to the electrode. The electrode includes one or moresensors coupled to a sensor display. The energy source may include or becoupled to a return electrode.

In another embodiment, the electrode includes a multi-cellular structurethat is configured to expand radially outward. The electrode includes atip portion configured to self center the electrode within a pulmonaryvein with a proximal portion of the electrode configured to abut againsttissue adjacent the ostium of the pulmonary vein.

In another embodiment, the tip portion includes a first lumen and asecond lumen, wherein the first lumen coincides with the lumen of thecatheter and the second lumen is positioned adjacent the first lumen andis configured to engage a guide wire in facilitating access to the leftatrium of the heart. In still another embodiment, the ablation cathetersystem includes a push rod coupled to the electrode and is configured tostabilize the electrode.

In another embodiment, the present invention is directed to an electrodecoupled to an ablation catheter system configured to ablate tissueadjacent an ostium of a pulmonary vein in a left atrium of a heart. Theelectrode includes a frame including multiple struts defining centerportion cells, intermediate cells and outer cells. The intermediatecells being disposed between the center portion cells and the outercells, and further, the intermediate cells extending radially outwardfrom the center portion cells and the outer cells extending radiallyoutward from the intermediate cells. With this arrangement, the frame isconfigured to move between a constricted narrow configuration and aradially self expanding configuration. Further, in one embodiment, theframe is configured to self expand to a conical configuration.

In another embodiment, the electrode includes center portion cellshaving common struts with the intermediate cells. In still anotherembodiment, the intermediate cells include common struts with the centerportion cells and the outer cells.

In still another embodiment of the electrode, the outer cells includeattachment structures, such as eyelets, configured to attach linesextending to the ablation catheter system.

In another embodiment, the frame is configured to self expand with aflange portion. Such a flange portion can be defined from at least oneof the outer cells and the intermediate cells of the frame. The centerportion cells can include a tip portion of the self expandedconfiguration of the electrode. Further, the tip portion is configuredto self center the frame over the ostium of the pulmonary vein.

In another embodiment, the frame includes one or more sensors configuredto sense characteristics of tissue adjacent the ostium of the pulmonaryvein. In still another embodiment, the frame comprises a super elasticmaterial.

In yet another embodiment, a catheter system for heating tissue adjacentan ostium of a pulmonary vein is provided. The system includes acatheter having a proximal portion and a distal portion. An RF energysource is operatively connected with the catheter and an electrodecoupled to the RF energy source. The electrode is positioned adjacentthe distal portion of the catheter and configured to heat at least onesegment adjacent the ostium of the pulmonary vein.

In accordance with another embodiment, a method of ablating tissueadjacent an ostium of a pulmonary vein is provided. The method includesdisposing an electrode adjacent a pulmonary vein and placing a centeringdevice at least partially within the pulmonary vein. The electrode ispositioned against tissue at or near the ostium of the pulmonary veinsubsequent placing the centering device and Energy is provided to theelectrode to ablate the tissue contacted by the electrode.

In accordance with another embodiment, a method of ablating tissueadjacent an ostium of a pulmonary vein is provided. The method includesdisposing an electrode adjacent a pulmonary vein. Tissue is contactedwith the electrode electrical characteristics of the tissue are measuredthrough the electrode. The electrode is positioned in response to themeasured electrical characteristics and tissue is ablated with theelectrode.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 shows a catheter system configured to enter the left atrium ofthe heart to ablate tissue adjacent the pulmonary vein, according to anembodiment of the present invention;

FIG. 2 shows the catheter system in FIG. 1 with a self expandingelectrode deployed from the catheter system, according to an embodimentof the present invention;

FIG. 3 is a partial cross-sectional view depicting another embodiment ofthe self expanding electrode with a pusher rod integrated with thecatheter system, according to another embodiment of the presentinvention;

FIG. 3A is a partial cross-sectional view depicting the electrode ofFIG. 3 in a constricted configuration being recaptured by the catheter,according to an embodiment of the present invention;

FIGS. 4 and 5 illustrate top and perspective views of the self expandingelectrode, according to an embodiment of the present invention;

FIGS. 6 and 7 illustrate top and perspective views of the self expandingelectrode in a substantially flat configuration, according to anotherembodiment of the present invention;

FIGS. 8A-8C illustrate an electrode according to an embodiment of thepresent invention;

FIGS. 9 and 10 illustrate electrodes according to additional embodimentsof the present invention;

FIG. 11 shows an electrode with an expansion device according to anembodiment of the present invention;

FIG. 12 shows an electrode according to yet another embodiment of thepresent invention;

FIGS. 13 and 14 show electrodes utilized with centering devicesaccording to an embodiment of the present invention;

FIGS. 15A and 15B illustrate electrodes according to additionalembodiments of the present invention;

FIGS. 16A and 16B illustrate electrodes according to additionalembodiments of the present invention;

FIGS. 17A and 17B show an electrode and catheter system according to anembodiment of the present invention;

FIG. 18 shows an electrode according to another embodiment of thepresent invention:

FIGS. 19A-9C show an electrode and catheter system according to anotherembodiment of the present invention;

FIGS. 20 and 21 show electrodes according to additional embodiments ofthe present invention; and

FIG. 22 shows a catheter system in accordance with another embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIG. 1, a catheter system 10 is shown which isconfigured to enter a left atrium of the heart (not shown) according toan embodiment of the invention. Such a catheter system 10 includes anelectrode 50 that is sized and configured to ablate tissue at the ostiumof the pulmonary vein within the left atrium of the heart. The cathetersystem 10 includes a handle 12, a catheter 20 and the electrode 50disposed within a tip portion 22 of the catheter 20. The catheter system10 may also include an energy source 14, a return electrode 16 and asensor display 18 configured to display information being received fromone or more sensors within or near the electrode 50. The catheter system10 of the presently considered embodiment is configured to be employedas an ablation catheter under a uni-polar system, utilizing the returnelectrode 16. However, as will be recognized by one of ordinary skill inthe art, the ablation catheter of the present invention can be utilizedas a bi-polar system with minor modification.

Use of RF energy and associated electrodes is discussed in substantialdetail in Applicants previously filed U.S. patent application Ser. No.11/754,978, filed May 29, 2007, entitled METHODS, SYSTEMS, AND DEVICESFOR SENSING, MEASURING, AND CONTROLLING CLOSURE OF A PATENT FORAMENOVALE, the disclosure of which is hereby incorporated by reference inits entirety, as well as Applicants previously filed U.S. patentapplication Ser. No. 11/754,963, filed May 29, 2007, entitled METHODS,SYSTEMS, AND DEVICES FOR CLOSING A PATENT FORAMEN OVALE USING MECHANICALSTRUCTURES, the disclosure of which is hereby incorporated by referencein its entirety.

The handle 12 may include an actuator 24 configured to deploy theelectrode 50 from the catheter 20 as well as recapture or re-sheath theelectrode 50 within the catheter 20. The catheter 20 includes a proximalportion 26 and a distal portion 28 with a lumen 30 extending through thelength of the catheter 20. At the proximal portion 26 of the catheter20, the catheter 20 is incorporated with the handle 12. The distalportion 28 of the catheter 20 includes the tip portion 22. The tipportion 22 may include a lumen that extends from, and coincides and isin communication with, the lumen 30 of the catheter 20. Such tip portion22 is configured to house or hold the electrode 50 in a constricted andcontained configuration. The electrode 50 is interconnected to thehandle 12 via lines 32 (or tethers) and a push rod (see FIGS. 3 and 4)that can extend through a portion of, or fully through, the length ofthe lumen 30 of the catheter 20. The tip portion 22 may also include arapid exchange (Rx) lumen 34 to facilitate accessing the left atrium ofthe heart via a guide wire (not shown). Such an Rx lumen 34, disposed ina non-coaxial arrangement with the lumen 30 of the catheter 20 or tipportion 22, is fully disclosed in Applicant's previously filed patentapplication, U.S. patent application Ser. No. 11/836,051, filed Aug. 8,2007, the disclosure of which is hereby incorporated by reference in itsentirety. It is also noted that the currently described catheter system10 may also be adapted to facilitate over the wire access to the leftatrium of the heart.

Referring now to FIGS. 1 and 2, the catheter system 10 may be seen withthe electrode 50 in a non-deployed position (FIG. 1) and a deployedposition (FIG. 2). To deploy the electrode, the actuator 24 on thehandle 12 can be manually moved as shown by arrow 36 from the positionshown in FIG. 1 to the position shown in FIG. 2. A push-rod (not shownin FIGS. 1 and 2) may be associated with the actuator 24 to displace theelectrode 50 in relationship to the tip 22 of the catheter 20. Inanother embodiment, the actuator 24 may be configured to move thecatheter 20 proximally (relative to a push-rod or other structure) tofacilitate un-sheathing the electrode 50 from the tip portion 22 of thecatheter 20.

As depicted, the electrode 50 can be configured to automatically selfexpand to an enlarged, un-constricted and expanded configuration. Suchexpanded configuration of the electrode 50 may include a conicalconfiguration or the like or any other shaped configuration, such aspartially conical with a proximal outward extending flange, that willmaximize the preferred area for ablating tissue at the ostium of thepulmonary vein. Further detail regarding the structure of the electrode50 will be discussed below. In addition, at a proximal side of theelectrode 50 there may be attachment points 52 for the lines 32 ortethers to couple thereto. The electrode 50 may be configured to movebetween a deployed configuration and the constrained non-deployedconfiguration within the tip portion 22. In addition to moving thecatheter 20 to deploy the electrode 50 as described above, the actuator24 may be utilized to displace the catheter 20 and recapture or resheaththe electrode 50. In another embodiment, the electrode may be configuredto be substantially flat when in a substantially unconstrained state. Insuch a case, the electrode may be configured to contact a greater areaof tissue surrounding the ostium of a pulmonary vein.

The catheter 20 can access the left atrium of the heart via a guide wire(not shown). As such, the guide wire can be pushed through the femoralvein to access the left atrium via a trans-septal puncture using, forexample, known techniques in the art. Once the guide wire has accessedthe left atrium, the distal portion 28 of the catheter 20 can thenaccess the left atrium by inserting the proximal end of the guide wirethrough the Rx lumen 34 of the tip portion 22. The catheter 20 is thenmoved distally through the vein to access the left atrium and theelectrode 50 may be deployed from the tip portion 22 of the catheter 20.The electrode 50 may be positioned over the ostium of the pulmonaryveins with a distal end of the electrode 50 extending within thepulmonary vein. In this position, the electrode 50 can be used tomeasure electrical signals of the muscle tissue with sensors on theelectrode 50 (or with the electrode itself). Such sensors can determinecharacteristics of the tissue. This sensing of the tissue can facilitatethe determination of which portion(s) of the tissue adjacent thepulmonary vein need to be treated and the proper position of theelectrode 50 for such treatment.

In one embodiment, the electrode 50 itself may be used as a sensor, withone or more additional electrodes (e.g., a return electrode 16) actingin concert with the electrode 50 positioned at or near the pulmonaryvein. In another embodiment, specific components or areas of theelectrode 50 may be electrically isolated from one another such that the“electrode 50” itself acts as multiple electrodes. The electrode 50 maybe used, for example, as an EKG electrode during one stage of theprocess while being used as a heating or ablating electrode duringanother stage of the process.

The one or more sensors (or electrodes) may be coupled to a controllerfor evaluating the electrical signals generated by such sensors. Thesensors may also be coupled to a display 18 to provide feed back to thephysician, based on the signals generated by the sensors, so thephysician may understand and evaluate the characteristics of the tissue.This further helps the physician in understanding what the properposition and orientation of the electrode 50 should be, as well as theamount of energy or heat that should be applied to the tissue, in orderto obtain the desired results from the ablative process. Once thephysician is able to evaluate the characteristics of the tissue, thephysician can then place the electrode 50 over the ostium and heat thetissue with RF energy (or other energy) via the energy source 14 in amanner consistent with that which was determined in the exploratory orinvestigative process.

In one embodiment, the electrode 50 may include a multi-cellularstructure and exhibit generally conical or other tapered configuration.Such an electrode 50 is configured to maximize the tissue area at theostium that is heated with the energy from the energy source 14.Further, according to the present invention, the generally conicalconfiguration of the electrode 50 provides an inherent self centeringfeature by positioning a distal tip of the conical structure within thepulmonary vein and moving the electrode 50 forward so that the electrode50 is positioned against the tissue adjacent the ostium of the pulmonaryvein. After heating the tissue, the electrode 50 can again be utilizedfor sensing the characteristics of the tissue in order to determine ifthe tissue has been sufficiently treated as desired. This process canthen be repeated in treating the tissue at the ostium for each of thefour pulmonary veins as determined from the electrode 50. Once complete,the electrode 50 can be recaptured within the tip portion 22 of thecatheter and withdrawn from the patient.

Referring to FIG. 3, a cross-sectional view of an electrode 50 is shownwherein a push rod 36 is utilized to assist in the placement andrecapture of the electrode 50 during an ablation procedure. Theelectrode 50 is coupled with a push rod 36 which may extend coaxiallywith an axis of the tip portion 22 of the catheter 20 (not shown in FIG.3). The push rod 36 may include a distal portion 38 configured to beattached with a center portion 40 of the electrode 50. In anotherembodiment, the push rod 36 may be attached to the electrode 50 by wayof generally radially-extending struts (not shown) in an umbrella-likeconfiguration. In such a configuration, the struts may be attachedsymmetrically to various intermediate portions of the electrode 50. Inanother embodiment, a strut configuration may be used in conjunctionwith (rather than in place of) attachment of the push rod 36 to thecenter portion 40 of the electrode 50.

The push rod 36 may be employed to provide a pushing force, indicated byarrow 42, when the electrode 50 is positioned over the ostium of thepulmonary vein. In addition, as depicted in FIGS. 3 and 3A, the push rod36 can be utilized to act in conjunction with the tethers or lines 32when recapturing the electrode 50 within the tip portion 22 of thecatheter 20. More specifically, the lines 32 may be coupled to theproximal attachment points 52 of the electrode 50 and extend proximallythrough, for example, an inner sheath 44 or ring. In this manner, thepush rod 36 can be used as leverage to hold the distal portion of theelectrode 50 steady while the lines 32 are moved proximally (or theinner sheath 44 is moved distally—or both), thereby, pulling theproximal attachment points 52 or ends of the electrode 50 in a radiallyconstricted and narrow configuration to be recaptured within the tipportion 22 of the catheter 20.

Referring now to FIGS. 4 and 5, the electrode 50 is shown and describedin further detail according to one embodiment of the invention. Theelectrode 50, exhibiting a generally conical or tapered configuration,may include a distal portion 54, which may also be referred to as a tipportion (and may correspond to the center portion 40), and a proximalportion 56 being at an opposite end of the electrode 50. The proximalportion 56 is radially expanded as compared to the distal portion 54.The radially expanded proximal portion 56 may include the attachmentpoints 52 in the form of, for example, eyelets, for attachment of thelines (see, e.g., FIGS. 2 and 3).

In one embodiment, the electrode 50 may be formed from a flat sheet ofsuper elastic material, such as Nitinol material. For example, theelectrode 50 can be laser cut from such flat sheet of material and thenshaped or heat set to the desired configuration. Such heat setting canbe employed in, for example, a heated sand bath utilizing techniquesknown to those of ordinary skill in the art. It should be noted that theelectrode may include, or be formed from, other materials as known inthe art.

FIGS. 6 and 7 illustrate the electrode 50 during manufacturing thereofprior to shaping or heat setting the electrode such that it exhibits agenerally conical configuration. As previously noted, the electrode maybe formed from a flat sheet of Nitinol or other appropriate material. Inone example, a laser cutting process and an electro polishing processmay be used to cut and form the initial configuration of the electrode.Of course, other processes known to those of ordinary skill in the artmay similarly be used. The electrode may be formed as a unitarystructure. In one embodiment, the electrode 50 can be formed, via a heatsetting process, to provide a self expanding conical configuration. Inother words, the electrode may be deformed to a constrainedconfiguration (e.g., when stored within the catheter tip prior todeployment) and expand into a desired shape (e.g., generally conicalwhere the proximal end 56 extends radially further than does the distalend 54) upon release from a constricting force (again, such as whenreleased from the catheter tip). In another embodiment, the electrode 50may self expand from a constricted or collapsed configuration to asubstantially flat shape (i.e., the radially outer portion and thecenter portion lie substantially within the same plane) and be utilizedto ablate tissue surrounding the ostium of the pulmonary vein.

It is further noted that, in one embodiment, the electrode 50 may beselectively configured, in terms of shape, size and orientation, duringuse thereof. For example, the electrode 50, may be used in a flatconfiguration to treat an area surrounding the ostium of a pulmonaryvein, it may be used in a conical configuration to treat a portion ofthe pulmonary vein or the ostium itself, or it may be selectivelyconfigured to exhibit a desired amount of taper between a “flat”configuration and a fully deployed conical configuration. Selectivelyconfiguring the geometry of the electrode further enables tailoring ofits placement so that ablation of specific tissue may be accomplishedmore effectively. Such selective configuring may be accomplished, forexample, by manipulating the push rod 36 and lines 32 to effect adesired configuration.

As shown in FIGS. 6 and 7, an electrode 50 may include a frame 60 havingmultiple cells or a multi-cellular configuration. The multi-cellularconfiguration can include center portion cells 62, intermediate cells 64and outer cells 66 each being defined by multiple struts 70, thecombination of struts 70 and cells (62, 64 and 66) defining the frame 60or at least a portion thereof. In one embodiment, the center portioncells 62 may collectively exhibit a flower like configuration. Thecenter portion cells 62 may include free ends 68 that each extend towarda center 76 or axis of the frame 60. In such an embodiment, such centerportion cells may be considered to be “open” cells since the free ends68 are not joined to form a closed periphery. during use of theelectrode 50, one or more of the free ends 68 may be coupled to the pushrod (FIGS. 3 and 3A) for deployment and recapture purposes as discussedabove. In another embodiment, the ends of the center portion cells maybe interconnected (i.e., not free ends) to form a center cell and,therefore, defining closed periphery cells as the center portion cells62. In such a case, a push rod may be coupled to a portion of theperiphery defining the center cell.

Still referring to FIGS. 6 and 7, the intermediate cells 64 may sharecommon struts 70 adjacent center portion cells 62. In other words, asingle strut 70 may be partially define a center portion cell 62 as wellas partially define an intermediate cell 64. Similarly, the intermediatecells 64 may share common struts 70 to both the center portion cells 62and the outer cells 66. In this manner, the center portion cells 62,intermediate cells 64 and the outer cells 66 build upon each other in aradially outward and symmetrical arrangement. It is noted, however, thatasymmetrical configurations are also contemplated. Attachment points 52,which may include, for example, an eyelet, may be formed or coupled to aportion (e.g., a radially-most outward portion) of the outer cells 66for coupling the distal ends of the lines or tethers (see e.g., FIGS. 2and 3). The frame 60 may also include markers (not shown), such asradio-opaque markers or other markers known in the art, for imagingpurposes.

In addition, the struts 70 defining the center portion cells 62 may besymmetrical to one another. Likewise, the struts for the intermediatecells 64 may be symmetrical with each other and the struts 70 for theouter cells 66 may be symmetrical with one another. With such anarrangement, the electrode 50 can symmetrically expand and constrict,thereby limiting the strain and stress placed on the struts 70 whenmoving between an expanded and constricted configuration. Furthermore,the frame 60 can be sized and configured such that the struts 70 foreach of the cells can include tapered portions so as to manipulate thebehavior of the frame 60, while maintaining structural integrity, whenthe frame or electrode is moved between the deployed configuration andthe constrained configuration within the tip portion of the catheter 20.In other words, a strut may change in cross-sectional area (takensubstantially transverse to its length) as it extends along its length.Further, the aspect ratio of a depth 72 and a width 74 of the struts canbe manipulated to increase the structural integrity of the frame 60 whenbeing moved between expanded and constricted configurations.

Referring now to FIGS. 8A-8C, an electrode 100 is shown in accordancewith another embodiment of the present invention. The electrode 100 maybe formed from a tube having cuts or slits 102 formed along a portion ofits length. The cuts or slits 102 define strut members 104. Theelectrode 100 may take the form as shown in FIG. 8A when disposed withina catheter (not shown) for delivery to a desired location within apatient's heart. When in the delivery configuration, the struts 104 aresubstantially elongated. When deployed, the longitudinal ends 106 and108 of the electrode 104 may be displaced toward one another (such as bypush rods, tethers and the like) such that the struts 104 become curvedor bent and have portions displaced radially outward as indicated inFIGS. 8B and 8C. The radially outward portions of the struts 104 maythen be used to contact a desired area within the heart, such as thepulmonary vein, the ostium of the pulmonary vein or surrounding tissue.When the ablation procedure is complete, the electrode 100 may berecaptured within a catheter by displacing the ends 106 and 108 awayfrom each other so that the struts 104 are again elongated (such asshown in FIG. 8A) and electrode may be drawn back into the catheter. Itis noted that a similarly shaped electrode may be formed by other meanssuch as by use of wire or other material wherein the electrode is selfexpanding to the configuration shown in FIGS. 8B and 8C. While fourstruts are shown to be used in FIGS. 8A-8C, such is not to be consideredlimiting and other numbers of struts are contemplated as being utilized.

Referring briefly to FIG. 9, another electrode 110 is shown whichexhibits a configuration of a substantially helical coil. A similarlyshaped electrode 120 is shown in FIG. 10. The electrode 110 of FIG. 9 isconfigured to be a connected at a proximal end 112 thereof, while theelectrode 120 of FIG. 10 is configured with a connection at a distal end122 thereof. Such electrodes 110 and 120 may be formed of wire, a shapememory alloy, or from other appropriate material.

Referring briefly to FIG. 11, an electrode 130 is shown having anexpansion device 132 associated therewith. The expansion device 132 mayinclude, for example, a balloon or self-expanding foam. The use of anexpansion device 132 may assist in expanding the electrode and effectingcontact of the electrode with the surrounding tissue. Additionally, theexpansion device 132 may be used to help center or otherwise positionthe electrode with respect to the pulmonary vein 134.

FIG. 12 shows another embodiment of an electrode 140 that includesmultiple arms 142 shaped and configured to engage the ostium of apulmonary vein 134. The arms 142 may include distal portions 146 sizedand shaped to enter the pulmonary vein 134, while the arms 142 flareradially outwardly so as to have a portion of the electrode 140 that iswider than ostium and, therefore contacts or engages the ostium (and/ortissue surrounding the ostium) of the pulmonary vein 134.

Referring briefly to FIG. 13, an electrode 150 is shown that isassociated with a centering device 152. The centering device 152 mayinclude, for example, expandable foam, a balloon, or some other body orresilient material. The centering device 152 may be disposed within thepulmonary vein 134 so as to assist in positioning the electrode 150 at adesired location. The electrode may be configured according to any ofthe various electrodes described herein or even according to knownelectrode configurations. For example, FIG. 14 shows a similar mechanismhaving a centering device 152 with a differently configured electrode160. The electrode shown in FIG. 14 includes a generally ring shapedstructure which may be configured as an open loop 162 with a single endof the electrode 160 extending through the catheter 164, as shown inFIG. 15A, or as a closed loop 166 with two ends of the electrodeextending into the catheter 164, as shown in FIG. 15B.

Referring briefly to FIGS. 16A and 16B, further embodiments ofelectrodes 170 and 180 are shown. The electrodes 170 and 180 generallyhave multiple arms 172 and 182 shaped and configured to engage theostium of a pulmonary vein 134. The arms 172 and 182 may include distalportions 174 and 184 sized and shaped to enter the pulmonary vein 134,while the arms 172 and 182 flare radially outwardly so as to have aportion of the electrodes 170 and 180 that is wider than ostium and,therefore contacts or engages the ostium of the pulmonary vein 134. Theelectrode 180 shown in FIG. 16B is formed in a closed loop configurationas compared the electrode 170 shown in FIG. 16A.

Referring now to FIGS. 17A and 17B, an electrode 188 in accordance withanother embodiment of the present invention is shown. The electrode 188includes a radially expanding structure 190 such as a stent-like deviceor a resilient polymer structure. The radially expanding structure 190may extend along a push-rod 192 or other structure and be radiallyconstricted such that it fits within a lumen of a catheter 194. A distalend 196 of the radially expanding structure may be coupled with thepush-rod 192 while a proximal end 198 of the push-rod 192 may beconfigured, when released from the lumen of the catheter 194, to abutagainst a surface of the catheter 194. The catheter 194 and push rod 192may then be displaced relative to each other, such as shown in FIG. 17B,so that the radially expanding structure 190 becomes shortened andexpands radially. The electrode 188, having been expanded radially, nowcontacts tissue within the pulmonary vein 134, at the ostium, or both.The push-rod 192 may act as a centering device to help locate theelectrode 188 relative to the pulmonary vein 134. Tethers, or othermechanisms (not shown), may be coupled with the proximal end of theradially expanding structure 190 to help recapture the electrode forrepositioning or after an ablation process is complete.

Referring to FIG. 18, another electrode 200 may include a moreconventional stent-like device that is expanded, for example, by aballoon or other mechanism to engage tissue associated with a pulmonaryvein 134.

Referring to FIGS. 19A-19C, an electrode 210 according to anotherembodiment may include a spring 212 or other helical spring-likestructure contained within a lumen of a catheter 214. A push-rod 216 maybe coupled to a distal end of the spring 212 to assist in deploying thespring 212 from the catheter 214. While in the catheter 214, the spring212 may be radially constricted such that it expands radially whenreleased from the lumen as indicated in FIG. 19B. A proximal end of thespring 212 may then abut a surface of the catheter (e.g., an endsurface) and the catheter 214 and push-rod 216 may be displaced relativeto each other to shorten the length of the spring 212. Thelongitudinally compressed spring 212 may then be placed in contact withthe ostium of the pulmonary vein 134 as indicated in FIG. 19C. Theelectrode may be recaptured in a manner such as previously described. Itis noted that the electrode may also be deployed and recaptured bytwisting the ends of the spring 212 relative to each other so as toalter the diameter of the spring 212.

Referring briefly to FIG. 20 a annular electrode 220 is shown as anexample of a bipolar electrode having a conductive inner surface 222which may act as a first pole and a conductive outer surface 224 may actas a another pole. The two conductive surfaces 222 and 224 may beseparated from one another by a dielectric material 226. In such aconfiguration, separate leads from an RF generator, for example, may becoupled with the conductive surfaces 222 and 224 causing current to flowfrom one ring or surface (e.g., 222) to another (e.g. 224).

In another embodiment, as shown in FIG. 21, an annular electrode 230 maybe segmented longitudinally so as to have alternating poles around thecircumference of the electrode. The segments 232 are electricallyisolated from one another such that current flows from one segment,through tissue contacting or adjacent the segment, and to anothersegment of an opposite polarity.

In accordance with another embodiment, as shown in FIG. 22, acapacitively coupled electrode is shown wherein a segmented catheter 240is placed adjacent tissue to be ablated. A selectively positionedelectrode 242 is positioned within the catheter 240 providing aselectively adjustable ablation point. The ablation point is determinedby the relative location of between electrode 242 and the segmentedcatheter 240. Thus, the ablation point may be adjusted by repositioningthe electrode 242 within the catheter 240. Such an embodiment might beconfigured to utilize either a unipolar or bipolar electrode.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the inventionincludes all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. An electrode configured to be coupled to an ablation catheter systemconfigured to ablate tissue adjacent an ostium of a pulmonary vein in aleft atrium of a heart, the electrode comprising: a frame includingmultiple struts defining center portion cells, intermediate cells andouter cells, the intermediate cells being disposed between the centerportion cells and the outer cells, the intermediate cells extendingradially outward from the center portion cells and the outer cellsextending radially outward from the intermediate cells, the frameconfigured to move between a constricted narrow configuration and aradially self expanded configuration.
 2. The electrode of claim 1,wherein the frame is configured to self expand to a substantiallyconical configuration.
 3. The electrode of claim 1, wherein the centerportion cells include common struts with the intermediate cells.
 4. Theelectrode of claim 3, wherein the intermediate cells include commonstruts with the outer cells.
 5. The electrode of claim 1, furthercomprising eyelets adjacent the outer cells configured for attachment tolines extending from a catheter of the ablation catheter system.
 6. Theelectrode of claim 1, wherein the frame comprises one or more sensorsconfigured to sense characteristics of tissue adjacent the ostium of thepulmonary vein.
 7. The electrode of claim 1, wherein the center portionis sized and configured to be at least partially disposed within apulmonary vein.
 8. The electrode of claim 1, wherein the center portioncells are configured to self expand to a tip portion, the tip portionconfigured to self center the frame over the ostium of the pulmonaryvein.
 9. The electrode of claim 1, wherein the frame comprises a superelastic material.